Thirsty turfgrass may benefit from compost & fertilizer

Turfgrass is big business – but keeping it both healthy and looking healthy requires a certain amount of water, which can become scarce in certain areas and certain seasons.

Water restrictions and rising costs require more sustainable solutions to improve water efficiency without compromising turf performance. A team from the University of Florida’s Institute of Food & Agricultural Sciences (UF/IFAS) has shown that incorporating compost can enhance soil structure, increase plant-available water and potentially reduce irrigation needs for warm-season turfgrasses, such as St. Augustine grass, which they studied.

The grass’s seeds, part of the Poaceae family, have only recently become commercially valuable and viable, so it’s typically propagated by plugs, sprigs or sod. Once the grass is cultivated, it can propagate on its own. It’s found throughout much of the Southeast. It features deep green and blue-green color and thrives in warm and humid environments. It’s a perennial and coarse-textured turfgrass.

Jaspal Singh, a graduate research assistant in UF/IFAS, presented work titled “Improving Turfgrass Vitality & Irrigation Efficiency with Compost Amendments” at the most recent American Society for Horticultural Science meeting. His co-authors were Alex Lindsey, Eban Bean, Natasha Restuccia and Victor Abarca.

Singh’s team wanted to see how compost and fertilizer applications impacted turfgrass quality under varying irrigation conditions, specifically on the ‘Floratam’ cultivar. There were six different management practices studied:

• A control with neither compost nor fertilizer

• Compost topdressing once per growing season

• Combined compost topdressing and fertilizer application once per season

• Compost topdressing twice per season • Both compost and fertilizer applied twice per season

• Fertilizer alone applied twice per season On top of these, irrigation was applied at 50%, 75% and 100% of UF/IFAS recommendations for St. Augustine grass. Compost was applied at 0.5 cubic yards for every 1,000 square feet, and fertilizer was applied at 1 lb. N for every 1,000 square feet.

The researchers used visual assessments, normalized difference vegetation index (NDVI) imaging and soil moisture checks to figure out which combinations worked best for healthy turf.

It turns out that single applications of compost and fertilizer are not enough. The grasses that received compost twice, fertilizer twice and the combination of compost + fertilizer twice had better turf quality in both 2023 and 2024 across the 75% and 100% irrigation levels. The same was true with soil moisture. In this case, more was better.

Singh noted that in general, the combined applications of compost with fertilizer applied twice provided the best benefits and quality. This combined treatment significantly enhanced soil moisture retention compared to both the fertilizer only and control treatments.

However, water is still a must for ‘Floratam.’ A 50% reduction in irrigation negatively affected turf quality and percent cover throughout the growing season. The grass can perform well with less irrigation, but not half of what it usually needs.

by Courtney Llewellyn